Respiratory apparatus commonly have devices to alter the humidity of the breathable gas in order to reduce drying of the patient's airway and consequent patient discomfort and associated complications. The use of a humidifier placed between the positive airway pressure (PAP) device and the patient mask produces humidified gas that minimizes drying of the nasal mucosa and increases patient airway comfort.
Many humidifier types have been proposed, including humidifiers that are either integrated with, or configured to be coupled to, the respiratory apparatus. Independent humidifiers have also been proposed. While passive humidifiers can provide some relief, generally a heated humidifier is required to provide sufficient humidity and temperature to the air so that the patient will be comfortable.
Humidifiers typically comprise a water tub having a capacity of several hundred millilitres, a heating element for heating the water in the tub, a control to enable the level of humidification to be varied, a gas inlet to receive gas from the PAP device, and a gas outlet adapted to be connected to a gas conduit that delivers the humidified, pressurized flow of breathable gas to the patient's mask.
Commonly, humidifier tubs are attached either directly to a humidifier control base or to a system base, or cradle, that facilitates the correct assembly of the PAP device with the humidifier. Generally, the humidifier control base or the system base, or cradle, comprises a heating plate that contacts the base of the humidifier tub to facilitate heating of the water within the humidifier tub.
FIG. 1 depicts a prior art humidifier device 10 with a control base 16, which comprises a heater plate 18. A water tub 12 comprising an air inlet 20, an air outlet 22 and a heat conductive tub base 14, is adapted to sit upon the heater plate 18 of the control base 16. The base systems typically comprise a spring loaded heater plate 18 on to which the water tub 12 is attached. The spring loaded heater plate 18 ensures good thermal contact with the tub base 14 of the water tub 12, although some thermal losses occur between the heater plate 18 and the water tub 12. For example, the Fisher & Paykel HC200™ system and the Respironics RemStar™ heated humidifier have spring loaded heater plates. However, such spring loaded heater plates can provide a friction force against insertion of the water tub, which may make installation of the water tub difficult for some users, especially older or frail users.
The water in the water tub 12 is heated via thermal conduction between the heater plate 18 and the tub base 14 of the water tub 12. The tub base 14 is commonly formed of aluminium or stainless steel. The tub base 14 is generally formed as a separate component of the water tub 12 and sealingly coupled to the upper portion of the water tub, for example using adhesives or a stamped rolled edge. For example, see Applicant's WO 2007/019626 A1, the entire contents of which are incorporated by reference. This results in multiple components that require assembly during manufacture of the humidifier and increase the size and weight of the device. Furthermore, the assembled construction provides an increased risk of leakage between the sealed components.
Other forms of heaters are known but have rarely, or not at all, been used in commercially available respiratory humidifiers to date. One example is induction heaters as described in Applicant's WO 2007/101298 A1, the entire contents of which are incorporated by reference. Flexible layered heaters are also known and have been used in a range of applications including defogging mirrors, screens for televisions, video cameras & mobile phones and blanket heaters. For example, printed thick film heating elements that comprise conductive and resistive inks, such as carbon ink or silver ink, have been used. FIG. 2 shows the general construction of a printed thick film heating element 28 comprising a first film substrate layer 30 with a conductive and resistive inks layer 34 printed thereon and then a second film 32. The two films 30, 32 are laminated together with a pressure sensitive adhesive sandwiching the ink layer 34. The films are typically thermoplastic or thermoset polymers such as polyester or polyimide. Such flexible layered heaters may be attached to the required surfaces to provide the required heating function.
Many products are provided with labels attached to their surfaces. Labels are commonly used to provide decorative designs, branding, texture, instructions, warnings and other such graphical material to products. There are many different forms of product labels and techniques for attaching such labels to objects. In-mold labeling is a method used to attach the labels to the surface of a molded object wherein the label is attached within the wall of a molded object. In-mold labeling is used with blow molded and injection molded products such as toys, containers for cleaning products, motor oil, beverages and the like. The label is printed onto a film using known printing techniques such as flexography, offset, screen or hot stamping printing. U.S. Pat. No. 6,551,671 (Nishizawa et al.) describes a process for in-mold labeling.
FIG. 3 illustrates the general construction of an in-mold label 35 where a graphic 38 is printed upon a film 36. The formed printed film 36, 38 is placed and held within an open mold with the film 36 surface adjacent to the mold. The mold is closed and the hot mold resin 40, such as a plastic polymer, is extruded or injected into the mold to form the desired object shape with an integrally molded label. The film 36 is generally comprised of a polypropylene or polyethylene copolymer that comprises a heat-activated adhesive that facilitates attachment of the printed film within the wall of the molded object.
Conventional humidifiers have the disadvantage of many different components that require assembly and increase weight. The assembly of different components and the use of heater plates and tubs with conductive base plates provides an increased risk of water leakage. The present invention seeks to address one or more of these disadvantages or at least provide a reasonable alternative.